1. Field of the Invention
The present invention relates to lateral double diffused MOSFETs, and in particular relates to lateral double diffused MOSFETs with a silicon rich content dielectric layer.
2. Description of the Related Art
The advantages of high power integrated circuits include high resistance for high voltage and low conductive resistance. Because of the advantages of high power integrated circuits, it has been widely used in display driver IC devices, power supply IC devices, the communications fields, etc.
Conventional high power devices are provided with vertical double diffused MOSFETs (VDMOSFETs) and lateral double diffused MOSFETs (LDMOSFETs), wherein a double diffused MOSFET is a representative lateral structure and a trench power transistor is a representative vertical structure. The operation of the high power devices is the same as conventional MOSs, wherein a gate electrode is used as an external voltage to form an inverted layer below the gate electrode, thus allowing the inverted layer to connect to a source region and a drain region by forming a channel.
The operating efficiency of transistors can be improved by maintaining the threshold-voltage (Vth) stability of an LDMOS. However, for an LDPMOS, shifts in threshold voltage of LDPMOSs are a serious problem. While reduction of threshold voltage shifts has been disclosed by controlling the doping concentration of a gate oxide layer, the method does not completely mitigate the problem efficiently.
Accordingly, there is a need to develop a method for efficiently reducing threshold voltage shift.